FORT LAUDERDALE -- Three preschoolers who recently attended the Rainbow Learning Center tested positive for a sexually transmitted disease, police said on Friday.

Gonorrhea infections were found in the throats of three of the dozens of children examined at the Sexual Assault Treatment Center after the arrest two weeks ago of preschool owner John W. Shaver, 56, on five counts of possessing child pornography.

Police would not say whether the children who tested positive were male or female and would not give their ages.

``This is an ongoing investigation, and we can`t answer any questions about the investigation itself,`` police Capt. Bruce Smith said.

Police also would not say whether Shaver had tested positive for the disease. Detectives were careful to point out that there was no direct evidence linking the disease to the day-care center or to Shaver.

``Everybody has had contact with more than one person,`` said Sgt. David Geyer, who is investigating the case.

Shaver is being treated at the Crisis Stabilization Center in Pembroke Pines, following a suicide attempt on Feb. 2, and could not be reached for comment on Friday. He has repeatedly denied doing anything improper to children at his day-care center.

Neither Geyer nor Joanne Richter, director of the Sexual Assault Treatment Center, could say how the children could have become infected.

``The most likely hypothesis is they were forced to perform oral sex with the infected adult, most likely a male,`` said Dr. Sally S. Atherton, assistant professor of microbiology and immunology at the University of Miami School of Medicine. ``It`s not something you pass around. It`s a bacteria; it requires contact.``

The children have been treated, police said. Most cases of gonorrhea can be cured with penicillin or other antibiotics, especially if the disease is diagnosed early.

The three children were part of a ``risk`` group detectives identified from children who attended the center. Children who fit the risk group were identified in nude pictures seized from Shaver`s home, exhibited behavior associated with sexual abuse, such as bed wetting, or said that they had been improperly touched.

``We`re trying to ask the parents to remain as calm as possible,`` Richter said. ``If they have any questions they can come in or call us.``

Richter said the investigation to trace the source of the gonorrhea could take up to 10 days.

Police said they were being careful with the information they release about the case to prevent hysteria.

Police also are worried that the parents` concern and widespread media attention could turn the case into a shambles like the McMartin trial in California.

In that case, considered to be the country`s longest and most expensive criminal trial, Raymond Buckey, 31, and his mother, Peggy McMartin Buckey, 63, were acquitted of charges that they molested 11 children at their preschool in Los Angeles between 1978 and 1983. Raymond Buckey faces in the same case other counts on which the jury was unable to decide.

During the Buckeys` five-year trial, jurors heard 2 1/2 years of testimony, including repeated testimony from the children involved. Jurors acquitted the pair because of a videotape that led jurors to think that the children were coached in their testimony.

Geyer said: ``We encourage parents to exercise a great deal of patience. I recognize the difficulty, especially in this case.``

Police are continuing to examine the thousands of pictures found in Shaver`s home near the preschool, 1331 NE 16th Terrace, Fort Lauderdale. At least 20 children identified in the pictures attended the preschool, which was taken over by Shaver in 1985.

FINDING HELP

-- Parents whose children attended Rainbow Learning Center may call the Sexual Assault Treatment Center, 765-4124, to schedule physical exams to see whether the children have contracted a sexually transmitted disease.

-- Parents whose children have exhibited behavioral changes also may call the center.

-- Parents whose children were tested privately are required under Florida law to report positive test results to the Fort Lauderdale Police Department at 761-5510 or 761-5700.